1. Field of the Disclosure
The disclosure relates generally to data communications, and in particular, to providing a safe Single Source Multicasting (SSM) reporting scheme requiring little or no user configuration nor dependency on additional protocols.
2. The Prior Art
Audio/video and any other type of content traffic can be provided through Intranets and the Internet to homes and businesses via a mechanism called IP multicast in which the traffic is only sent once by the content source, and replicated by the network to all interested receivers. Typically, the traffic is requested by receivers using a protocol called the Internet Group Membership Protocol (IGMP). Via IGMP, a receiver specifies a so called IP multicast group G identifying the content the receiver is interested in (like a TV station) and, starting with version 3 of IGMP, optionally also the IP address of the content source.
FIG. 1 shows a diagram of a prior art multicasting system 100. A content source 105 with IP source address S is coupled to a network 110, such as the Internet, and is configured to stream content traffic to a group of receivers 140 using IP multicast group address G. Typically, the receivers 140 are coupled to the network 110 through a Local Area Network (LAN) 150, such as an Ethernet network, which is coupled to the Internet through router 120.
In a typical example, one or more of the receivers Rn on the network 140 desire to acquire content provided by the source 105.
As is known in the art, IP multicast are packets are transmitted with a pair of addresses in the form of (S,G), where S is the source address, and G is the address defining a group of destinations, such as the group of receivers 140. Typically, the address range for S is from the IP address 1.0.0.0 to 223.255.255.255 and the address range for G is from the IP address 224.0.0.0 to 239.255.255.255.
When a receiver 140 desires to receive content from the source 105, it will send IGMP messages towards router 120 to indicate the content it is interested in group address. The router 120 and other routers within the network cloud 110 will use IP multicast routing protocols to acquire the content, and send it into LAN 150. The content will be available to all systems connected to the LAN; thus, those receivers who do not desire the content will simply ignore the content.
Router 120 and the other routers in 110 can run one of two forms of IP multicast routing: Any Source Multicast (ASM) or Source Specific Multicast (SSM). If they run ASM, it is sufficient for router 120 to receive IGMP messages from receivers on 150 that do only contain the group address G, the source address S is optional. If they run SSM then router 120 must receive IGMP messages with both the IP multicast group address G and the IP source address S, or else router 120 and routers in 110 will not be able to correctly forward the content to LAN 150.
FIG. 2 contains the structure of FIG. 1 and further includes an L2 switch 130 provided to more efficiently manage bandwidth on the access network 150. To prevent content from clogging the ports of receivers, networks typically include the L2 switch 130, also known as a LAN switch, which is a device configured to direct traffic only towards interested ports.
This directing may be accomplished through IGMP “snooping”, where L2 switch passively listens to IGMP messages and learns about the traffic demands on the host(s). L2 switches are typically designed to be a plug-and-play product that requires little or no user configuration.
Further versions of the IGMP protocol have attempted to add features and functionality. For example, IGMP version 2 can only provide for Any Source Multicasting (ASM), which accepts traffic from any source.
IGMP version 3 defines two types of requests. One host request is a group request that specifies a particular source be included, i.e. [G, INC{Sn}]. Another request is a group request that excludes a particular source, i.e. [G, EXL{Sn}].